Surfactants having fluorinated alkyl chains (hereinafter referred to as “fluorine-containing surfactant”) can effect various surface modifications due to the peculiar properties (water repellency, oil repellency, lubricity, antistatic property, etc.) of the fluorinated alkyl chains, and are hence employed in the surface treatment of a wide variety of base materials, such as fibers, cloth, carpets and resins. Further, when a fluorine-containing surfactant is added to an aqueous medium solution of substrate of varied type, not only can a uniform coating film free from crawling be formed at the time of coating film formation but also an adsorption layer of surfactant can be formed on the surface of the substrate, to thereby cause the surface of coating film to have the above peculiar properties of fluorinated alkyl chains.
Also in photographic light-sensitive materials, various surfactants are used and play important roles. Photographic light-sensitive materials are usually produced by separately coating a plurality of coating solutions including an aqueous solution of a hydrophilic colloid binder (e.g., gelatin) on a support, to form multiple layers. Multiple hydrophilic colloid layers are often simultaneously coated as stacked layers. These layers include antistatic layer, undercoat layer, antihalation layer, silver halide emulsion layer, intermediate layer, filter layer, protective layer and so forth, and various materials for exerting functions of the layers are added to the layers. Further, polymer latex may also be added to the hydrophilic colloid layer in some cases in order to improve physical properties of film. Furthermore, in order to add functional compounds hardly soluble in water, such as color-forming couplers, ultraviolet absorbers, fluorescent whitening agents and lubricants, to the hydrophilic colloid layer, these materials are sometimes emulsion-dispersed in a hydrophilic colloid solution as they are or as a solution in a high boiling point organic solvent, such as phosphoric acid ester-series compounds and phthalic acid ester compounds, for the preparation of a coating solution. As described above, photographic light-sensitive materials are generally constituted by various hydrophilic colloid layers, and in the production of them, it is required to uniformly coat coating solutions containing various materials at a high speed without defects such as repelling and uneven coating. In order to meet such requirements, a surfactant is often added to a coating solution as a coating aid.
Meanwhile, photographic light-sensitive materials are brought into contact with various materials during production, light exposure, and development thereof. For example, when a light-sensitive material is in a rolled shape in process steps, a back layer formed on the back surface of the support may contact with the surface layer. Further, when it is transported during process steps, it may contact with stainless steel rollers, rubber rollers, and the like. When they are brought into contact with these materials, surfaces (e.g. gelatin layer) of the light-sensitive materials are easily charged positively, and they may cause unnecessary discharge under certain circumstances. Therefore, there may remain undesirable traces of light exposure (called static marks) on the light-sensitive materials. Examples of methods of reducing this electrification property of gelatin include the prevention of the electrification (reducing an amount of electrification charged), making the accumulated charges leak easily, and the like. In order to prevent the electrification, a compound containing a fluorine atom is effective, and a specific fluorine-containing surfactant is often added.
In addition, reduction in surface resistance of a light-sensitive material by addition of a surfactant containing polyethylene (alkylene) oxide is frequently adopted as a method to achieve easy leakage of accumulated charges. More specifically, nonionic surfactants, containing both a fluorine atom and polyalkylene oxide in one molecule, are known (see, for example, in JP-A-2002-116520 (“JP-A” means unexamined published Japanese patent application)). Depending on the media to which such a method is applied, however, those surfactants cannot always produce sufficient effects. Therefore, further improvement has been needed.
On the other hand, it has been suggested that surfactants derived from perfluorooctanesulfonic acid prepared by electrolytic fluorination (as disclosed, e.g., in WO 02/092719), which have so far been used for general purposes, have a strong tendency to accumulate in ecosystems and raise safety concerns. As such, there is a need to develop fluorine-containing surfactants reduced in environmental load.